When discussing the two styles of sealing heads, tunnel & flat, it is important to remember a few important concepts:

1. The strength of the electromagnetic field generated by your induction sealer dissipates exponentially with respect to the distance from the sealing head.

2.The distance from the top of your cap to the foil inside the cap is not equal with all closure styles. Compare a flat continuous thread(CT) cap with a child resistant closure(CRC.) The foil in the flat CT cap is very near the top while the foil in the CRC maybe as much as 1/4" from the top of the cap!

3.The physical size of the foil inner liner plays a role in determining which style of sealing head works best for your application. While it may seem a little counter-intuitive at first thought, it takes more energy to seal a smaller liner than it does a large one. Because as the liner increases in size, it also increases the amount of metal mass available to be heated.

The tunnel sealing head was developed to address these concepts and is typically used in two situations. When the diameter of the foil liner is less than 53mm the tunnel sealing head allows us to most efficiently seal the package by directing the induction field from the top and sides of the container. Taller closures such as sports caps, push-pull, Yorkers and others place the foil relatively deep in the cap, so the induction field is directed from the sides to again efficiently seal the container.

An Enercon cap sealer with a
tunnel sealing head ensures
this package is hermetically
sealed to prevent leakage.